An example scheme of inspecting a flowability of a blood and a condition of a cell in the blood is a scheme of using a blood filter (see, for example, patent literatures 1 and 2). The blood filter includes a substrate formed with minute grooves and another substrate is joined with that substrate. When such a blood filter is used, a condition of a cell in a blood when the blood passes through the grooves can be observed.
FIG. 25 is a piping diagram showing an illustrative blood inspecting apparatus using the blood filter. A blood inspecting apparatus 9 includes a liquid feeding mechanism 91, a liquid discharging mechanism 92, a blood supply mechanism 93 and a flow speed measuring mechanism 94.
The liquid feeding mechanism 91 is for supplying a predetermined liquid to a blood filter 90, and includes liquid reserving bottles 91A, 91B and a liquid feeding nozzle 91C. The liquid reserving bottle 91A reserves an isotonic sodium chloride solution for measuring a flow speed of a blood. The liquid reserving bottle 91B is for reserving a distilled water used for rinsing pipings. According to this liquid feeding mechanism 91, as a three-way valve 91D is switched accordingly with the liquid feeding nozzle 91C being attached to the liquid filter 90, a state in which the isotonic sodium chloride solution is supplied to the liquid feeding nozzle 91C and a state in which the distilled water is supplied to the liquid feeding nozzle 91C can be selected.
The liquid discharging mechanism 92 is for discharging a liquid in the blood filter 90, and includes a liquid discharging nozzle 92A, a pressure-reduction bottle 92B, a pressure-reduction pump 92C and a liquid discharging bottle 92D. According to this liquid discharging mechanism 92, as the pressure-reduction pump 92C is actuated with the liquid discharging nozzle 92A being attached to the blood filter 90, a liquid in a piping 92E or the like is discharged in the pressure-reduction bottle 92B. The liquid in the pressure-reduction bottle 92B is discharged in the liquid discharging bottle 92D through a piping 92F by the pressure-reduction pump 92B.
The blood supply mechanism 93 suctions a liquid from the blood filter 90 to form a space for retaining a blood, supplies the blood in the space for retaining the blood, and includes a sampling nozzle 93A.
The flow speed measuring mechanism 94 is for obtaining information necessary for measuring a velocity of a blood traveling through the blood filter 90, and includes a U-tube 94A and a measuring nozzle 94B. The U-tube 94A is arranged at a position higher than that of the blood filter 90, and can cause the blood in the blood filter 90 to travel by a water head difference.
According to the blood inspecting apparatus 9, a traveling velocity of a blood is measured as follows.
First, as shown in FIG. 26, the interior of the blood filter 90 is replaced with an isotonic sodium chloride solution. More specifically, the liquid feeding nozzle 91C of the liquid feeding mechanism 91 is attached to the blood filter 90, and the three-way valve 91D is switched so that an isotonic sodium chloride solution in the liquid reserving bottle 91A can be supplied to the liquid feeding nozzle 91C. Meanwhile, the liquid discharging nozzle 92A of the liquid discharging mechanism 92 is attached to the blood filter 90, and the pressure-reduction pump 92C is actuated. Accordingly, the isotonic sodium chloride solution in the liquid reserving bottle 91A is supplied to the blood filter 90 through the liquid feeding nozzle 91C, and the isotonic sodium chloride solution passed through the blood filter 90 is discharged in the liquid discharging bottle 92D through the liquid discharging nozzle 92A.
Next, the liquid feeding nozzle 91C is detached from the blood filter 90, and as shown in FIG. 27A, some of the isotonic sodium chloride solution in the blood filter 90 are suctioned by the sampling nozzle 93A of the blood supply mechanism 93, and as shown in FIG. 27B, a space 95 for retaining a blood is formed.
Furthermore, as shown in FIG. 28A, a blood is collected from a blood collecting tube 96 by the sampling nozzle 93A, and as shown in FIG. 28B, a collected blood 97 is filled in the space 95 of the blood filter 90.
Subsequently, as shown in FIG. 29A, the measuring nozzle 94B of the flow speed measuring mechanism 94 is attached to the blood filter 90. Accordingly, by a water head difference caused between the U-tube 94A and the blood filter 90, the liquid in U-tube 94A travels toward the blood filter 90, and a liquid-level position in the U-tube 94A changes. According to the blood inspecting apparatus 9, as shown in FIG. 29B, a change speed of the liquid-level position in the U-tube 94A is detected by plural photo sensors 98, and based on the detection result, a travel speed of the blood is calculated.
As shown in FIG. 25, the flowability of the blood in the blood filter 90 can be observed on a monitor 99B as an imaging device 99A picks up an image of the blood filter 90.
According to the scheme of utilizing a water head difference between the U-tube 94A and the blood filter 90, however, a liquid-level position in the U-tube 94A changes, so that a measuring pressure (a pressure acting on a blood 97 in the blood filter 90) varies. Moreover, in order to cause the blood 97 to travel in the blood filter 90 by a water head difference, it is necessary that pipings 92E, 94C from the U-tube 94A to the pressure-reduction bottle 92D must be filled with a liquid. Hence, according to the blood inspecting apparatus 9, because a relatively long piping length is requisite, the piping resistance becomes large. Moreover, in addition to the liquid feeding nozzle 91C and the liquid discharging nozzle 92A, the measuring nozzle 94B for supplying a liquid from the U-tube 94A to the blood filter 90 is requisite, the number of nozzles for a measurement is large. Furthermore, because the number of nozzles is large, the pipings become complex, and the number of parts like the number of valves for switching the nozzles 91C, 92A, 93A, and 94B is also large, which interrupts miniaturization of the apparatus. The larger the number of parts becomes, the more a part with a relatively high failure rate like a valve is included, so that a mean-time-between-failure that is an index of representing a failure rate (a performance) of the apparatus becomes short.
In order to overcome such a problem, a straight tube arranged horizontally may be used instead of the U-tube 94A to maintain the water head difference at constant. In this case, however, because an effect to a measured value of a flow speed due to the inconsistency in the internal diameter of the straight tube per product becomes large, it is expected that the flow speed of a blood passing through the blood filter 90 cannot be figured out appropriately. In particular, when the internal diameter of the straight tube is set to be small in order to increase the travel speed of the fluid in the straight tube, the effect to the flow speed due to the inconsistency of the internal diameter becomes further large.
Moreover, according to a technique of detecting an interface between a liquid and a gas by a photo sensor 98, when the straight tube has a different internal diameter from those of the other pipings, a contact area of the gas with respect to the piping may change. In this case, if the contact area of the gas with respect to the piping changes when the travel speed of a blood is measured, the travel resistance of a fluid changes during a measurement of the travel speed. As a result, linearity in a relationship between the travel speed of the fluid and the travel time thereof is deteriorated, and it may become difficult to measure a precise travel speed.    Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. H02-130471    Patent Literature 2: Unexamined Japanese Patent Application KOKAI Publication No. H11-118819